The genetic makeup of all living organisms is contained in their DNA molecule. Replication occurs by the splitting of the DNA molecule, which duplicates itself through a transformation of its structure. Parts of the DNA molecule have been given names such as pyrimidine bases, cytosine, thymine or uracil that form a group of biochemicals that sustain life. The long DNA molecule holds itself together by using simple bonds like those found in sugars.
Researchers believe that the energy of the GUV photon causes the formation of a strong (covalent) bond to develop between specific biochemicals. However, the bond strength of the covalent bond is very dependent on the relative position of the participating atoms. When the bond is symmetrical on both sides of a hydrogen atom in the bond, it is referred to as a dimer. A dimer is a very strong bond and is not generally broken during the vaporization of the liquid. GUV light is known to produce Thymine, cytosine-thymine, and cytosine dimers. After the formation of the dimer, further replication of the DNA stops. FIG. 1 shows the concept of the dimer formation in a DNA molecule. Reports found in literature have demonstrated that UV photons at other wavelengths or low wavelength blue light can promote repair of the injured bonds and permit the organism to start replicating again. This is commonly referred to as photo-reactivation.
The DNA molecule absorbs light from about 180 nm to about 400 nm. The commercial germicidal lamps based on mercury excitation are used because they emit photons that are near the 260 nm absorption peak of DNA amino acids. The mercury gas and its pressure in the lamp determine the wavelength of the emitting light. For low-pressure (LP) and low-pressure high output (LPHO) lamps, the emitting wavelength is 254 nm. For medium pressure lamps, the emission ranges from 200 nm to above 400 nm. However, the strength of the emitted light is not effective below 245 nm for the continuous emitting lamps and below 235 nm for medium pressure lamps. Xenon gas in pulsed lamps produces a similar multi-wavelength emission to the medium pressure mercury lamps. However, critical to this patent is that the multi-wavelength source produces two different narrow spectral width (commonly referred to as single line) emissions that correspond to at least two peak absorption chromophores of the microorganism's DNA. This source is now referred to in the rest of the patent as a dual-single line lamp.
DNA action spectra show multiple peaks that are dependent on the composition of the nitrogenous bases and amino acids that make up the organism. While FUV photons have shown to be effective in breaking bonds, it is possible that the correct dual wavelength combination of FUV and UV-C could be just as or more effective. (See U.S. Pat. Pub US 2010/0028201.)
A recent technical paper (Peak et al, UV action spectra for DNA dimmer induction . . . , Photochemistry and Photobiology, 40, 5 (613-620), 1984) suggests that dimmer formation is not the only requirement to inactivate DNA. Absorption of different wavelength photons by different molecular groups in the long DNA molecule will enhance the energy transfer from group to group. Damaging or destroying these bond groups may be more effective in deactivating the DNA than with photons in a single band that affect only a few groups. No one has done a detailed study of the effectiveness of inactivation for the different single line UV emitters working in combination.
There are many articles about multi-photon effects on materials that can create different processes because different photon energies will resonate or create different energy levels in the electrons or atoms of the molecule. The concept in this specification is to use multiple narrow line wavelengths emitted from the same lamp to create multiple absorption pathway effects on microorganisms. It is conceivable that greater damage and a larger reduction in survival can occur since the multi-photon interaction could have more pathways to create its destruction. These pathways can occur simply by resonant absorption that causes a physical breaking of bonds in the pathways. It could also cause significant cross linking of different amino acids, nitrogenous bases, nucleotides and other critical bonds that permit the organism to replicate. Cross linking these bonds could and should create conditions that the organism could not replicate further and would reduce the transmission of these infectious agents to people in the area.
The energy of the emitted photon is determined by its wavelength. Photon energy is about 5 ev at 250 nm, and increases for shorter wavelengths. Different bonds in the DNA will be affected with photons of different energy.
The 540 kJ/mole photon energy from the FUV lamp exceeds the bond energies of many of the peptide bonds in proteins and those in nitrogenous bases of the DNA. The bacterial cell is surrounded by a lipid membrane or cellular wall that contains many protein molecules. The cell wall is essential to the survival of many bacteria. FUV light can damage the proteins in this structure whereas GUV can not. This should cause physical damage to the microorganism. FIG. 2 shows a micrograph of the Bacillus atrophaeus with magnification of 1000×. Photon impact resulted in ruptured sidewalls and organism segmentation that can be clearly seen in the 1000× frame. This is the first photographic evidence known that photons are actually causing damage and destruction to pathogens. A corresponding slide that received the same radiant exposure did not produce any replication indicating 100% kill of the organisms.
It has been fairly well established that the peptide bonds in all proteins are responsible for the peak absorption at two different wavelength regions; namely at 200 nm and at 280 nm. The peak absorption at either 200 nm and/or near 280 nm is also exhibited by all nitrogenous bases in the DNA as well as the proteins that form the outer cellular membrane of bacteria, spores and viruses. This occurs as well for nucleo-proteins, diglycine, triglycine, and bovine albumin (McLaren, et al, Photochemistry of Proteins and Nucleic Acids, Pergamon Press, Macmillan Company, 1964). Amino acids have a peak absorption band near 260 nm. A UV lamp emitting at 222 nm and/or 282 nm will produce the greatest photon absorption by the nitrogenous bases and proteins. A UV-C lamp emitting at 260 nm will produce the greatest photon absorption by the amino acids in the DNA. Consequently these three wavelengths are primary absorption bands that permit destruction of microorganisms.
Tests:
A number of comparative tests were done using three different microorganisms to test the concept. Petrie dishes were inoculated with each organism and exposed to different combinations of UV photons. The included figures show the same dish with light and dark background in order to get good contrast of the results.
FIG. 3 had Serratia marcescens as the test organism. The left side of the dish was exposed with a combination of 222 nm plus 254 nm photons. The right side of the dish was exposed with only 282 nm photons. The multi-wavelength side produced a significant improvement.
FIG. 4 had Aspergillus Niger as the test organism. The left side of the dish was exposed with only 282 nm photons. The right side of the dish was exposed with a combination of 282 nm plus 254 nm photons. The multi-wavelength side produced a significant improvement.
FIG. 5 had Escherichia coli as the test organism. The left side of the dish was exposed with a combination of 222 nm plus 254 nm photons. The right side of the dish was exposed with a combination of 282 nm plus 254 nm photons. The right side using the correct multi-wavelength combination of photons produced a significant improvement.
FIG. 6 had Planktonic Algae as the test structure. The left side of the dish was not exposed but the right side was exposed to FUV photons. Significant cellular damage occurred.
Analysis:
All tests were done using single line photon sources that emitted near the peak absorption of the two absorption bands of the DNA nitrogenous bases and the single absorption band of the DNA amino acids. This provided a true measure of the photon interaction for each of the different chromophore molecular groups and the interaction with other chromophore groups in the DNA molecule.
The results of the first three tests showed significant reduction in living organisms when multi-wavelength narrow line photons were used compared to single wavelength photons. These tests also demonstrated that the correct combination of dual-single line photons were significant and dependant on each organism. FIG. 6 demonstrates that the choice of wavelength is important. FUV photons produce significant cellular damage where GUV photons have little effect.
Similar tests done on pathogens would produce a list of the most effective combination of photon wavelengths that are effective in killing or deactivating each pathogen.